| BackgroundHypertension is a major risk factor of cardiovascular and cerebrovascular diseases.. Hypertensive left ventricular hypertrophy is one of the major cardiac changes and complications, and it is also an independent risk factor for cardiovascular events. The prevention and regression of LVH has become an important target in the treatment of hypertension. Researchs show that, pathogenic factor induced hypertensive left ventricular hypertrophy, such as hemodynamics, catecholamine and aldosterone neuro humoral factors can affect the characteristics of ion channels of myocardial cells, in a relatively short period of time so that the electrical remodeling. Hypertension induced left ventricular hypertrophy, due to the activation of neurohormonal hemodynamic load, and other factors caused by the long-term effect. Experienced by the normal configuration to left ventricular concentric remodeling, concentric hypertrophy and eccentric hypertrophy of the development process. ECG reaction is to change the heart electricity, electrocardiographic diagnosis of left ventricular hypertrophy and left ventricular high voltage electrical remodeling of the left ventricle is, cardiac ultrasound or magnetic resonance that is to change the heart morphology, heart ultrasound or MRI in the diagnosis of left ventricular hypertrophy is a reflection of the left ventricular structure remodeling. Electrical remodeling may be earlier than the structural remodeling, we speculated that the electrocardiogram can discover the change of hypertensive heart, early detect left ventricular hypertrophy reversal can be treated, but the related research has not been reported. ObjectiveTo reveal the sensitivity and specificity in the diagnosis of left ventricular hypertrophy by ECG. To explore whether ECG changes is earlier in left ventricular hypertrophy than ultrosoundcardiogram changes. And to further explore the significances of ECG in the early diagnosis of LVH. And to investigate hypertensive model method and rabbit blood pressure measuring method. Materials and methods40 male Japanese rabbits were randomly divided into 25 rabbits in hypertension group, and 15 rabbits in the control group. In hypertension group, 1cm above the renal artery coarctation of abdominal aorta, the diameter decreased from 50% to 60%, while the control group did not receive ligation, and the other treatment was the same as operation group. Were measured preoperatively electrocardiogram, ultrasound, blood pressure second week, fourth week,sixth week and eighth week after operation. In addition to the preoperative and postoperative eighth weeks underwent chest X-ray examination. Finally after killing the rabbits, we weigh the left ventricular mass, and do heart pathology. Results1. Blood pressure comparison. There was no significant difference in blood pressure between the two groups before operation(P > 0.05). At second weeks, fourth weeks, eighth weeks, sixth weeks, blood pressure in the experimental group was higher than that in the control group(P < 0.05). The blood pressure of rabbits was increased, and the time points were increased(P < 0.05).. There was no significant change in blood pressure of rabbits in control group(P > 0.05).2. Comparison of abdominal aortic ultrasonography. The experimental group coarctation degree maintained at a substantially constant range, narrow site and control group velocity faster, from the fourth week of the operation after gradually decreased(P < 0.05) compared. The internal diameter of the distal blood vessel increased gradually after the operation, but the blood flow velocity was lower than that of the stenosis, and decreased gradually from fourth weeks after surgery(P < 0.05). There were no significant differences in the diameter and blood flow velocity between the two groups of the rabbits in the control group(P > 0.05)..3. Comparison of cardiac ultrasonic measurements. Rabbits in experimental group, the left ventricular diastolic end diastolic diameter and left ventricular end systolic diameter at postoperative 4 weeks and preoperative difference was not statistically significant(P > 0.05), or slightly narrow, gradually increasing after 6 weeks after operation, and preoperative compared was statistically significant(P < 0.05). Left ventricular wall and left ventricular posterior wall and interventricular septum was thickened gradually trend, starting from 4 weeks after the operation is with the preoperative difference was statistically significant(P < 0.05); E / A after operation was gradually decreased, from 4 weeks after the start compared with the preoperative difference was statistically significant(P < 0.05). 4 weeks reduced to less than 1; left ventricular ejection fraction in the postoperative was gradually decreased, after eight weeks of operation and preoperative compared was statistically significant(P < 0.05). There were no significant differences in the preoperative and postoperative indexes of the control group(P > 0.05).. There were no difference in ultrasonic parameters between the two groups(P > 0.05) before operation. At the 2nd, 4th, 6th and 8th week, two groups of rabbits the except diastolic left ventricular ejection ejection fraction, left ventricular end diastolic diameter and left ventricular end systolic diameter and other echocardiographic parameters were statistically significant(P < 0.05).4. Comparison of ECG examination(1) Limb lead changes. In the experimental group, the R wave voltage and the QRS wave amplitude of standard lead II, standard in lead III and a VF showed a gradually increasing trend from postoperative 2 weeks began compared with preoperative had significant difference(P < 0.05); the R wave voltage and the QRS wave amplitude of standard leads I, a VL and a VR did not show obvious trend. In the control group, there was no obvious change in the amplitude of the QRS wave and the voltage of the R wave(P > 0.05) before and after the operation.. There were no significant difference in the lead parameters of the two groups before operation(P > 0.05). At the 2nd, 4th, 6th and 8th week, there were significant difference in the lead parameters of the two groups except for the lead and a VR lead parameters(P < 0.05).(2) Chest lead changes. In the experimental group, the QRS wave amplitude and the voltage of R wave in the chest were increased gradually, and there were statistically significant differences between the second weeks after operation and compared with the preoperative(P < 0.05).. There were no significant difference in the amplitudes of R and QRS waves between the two groups before operation(P > 0.05). At the 2nd, 4th, 6th and 8th week, the amplitudes of R and QRS waves in two groups of rabbits were significantly different(P < 0.05).(3) QRS duration and QTc changes. In the experimental group, the QRS time and QTc were gradually increasing, and the fourth weeks, sixth weeks and eighth weeks after operation were statistically significant(P < 0.05). There were no significant changes in the ECG parameters(P > 0.05) before and after operation in the control group.. There were no significant differences in the parameters of the two groups before operation(P > 0.05). At the 2nd, 4th, 6th and 8th week, the parameters of the two groups were statistically different(P < 0.05).5. Comparison of X-ray examination.Before the operation, there was no significant difference in cardiothoracic ratio(t = 1.299,P = 0.200). Operation group, eighth weeks after surgery in cardiothoracic ratio higher than preoperative(t = 3.067,P = 0.005). The control group preoperative and postoperative cardiothoracic ratio did not change significantly(t = 1.321,P = 0.200).6. Comparison of left ventricular mass index. The left ventricular mass index were(1.45 ± 0.36) g/kg and(1.02± 0.28) g/kg operation group, the left ventricular mass index higher than that of the control group(t = 2.680,P = 0.01).7. Pathological staining of myocardial tissues. After the two groups of rabbits were sacrificed, paraffin sections of the heart were taken and stained with HE. By Light microscope, control group showed normal myocardial cell size arranged in neat rows, and neat myocardial fiber, and the nucleus of the myocardium is oval in the center of the cell, without obvious myocardial interstitial hyperplasia. The volume of myocardial cells in experimental groups increased, and myocardial cell gap widened, and part of myocardial cells was dissolved, and another part of the myocardial cell showed vacuoles, fatty degeneration, myocardial fiber hyperplasia. Conclusion1. The lateral abdominal approach of coarctation of abdominal aorta in rabbit model of hypertension is feasible;2. Measurement of blood pressure in central ear artery of rabbit is feasible;3. The R wave voltage and QRS amplitude increase, and the duration of QRS wave and QTc prolong in the early stage of hypertension;4. In the early stage of left ventricular hypertrophy induced by hypertension, electrocardiogram changes should be earlier than structural changes under ultrasound;5. The electrocardiogram has certain value in the early diagnosis of hypertensive left ventricular hypertrophy. |
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